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Population dynamics and antagonistic potential of enterococci colonizing the phyllosphere of grasses
1Department of Agricultural Ecology, University of Rostock, Justus-von-liebig-Weg 8, D-18059 Rostock, Germany. edda.ott@agrarfak.uni-rostock.de
Aims:
To investigate the spatial and temporal dynamics of enterococci colonizing forage grass and their ability to produce bacteriocins.
Methods And Results:
Enterococci could be detected on above-ground plant parts throughout the growing season, with high continuity but low cell numbers (2.60 x 101-6.16 x 104 cfu g-1 fresh matter). A total of 750 strains were isolated and identified by their whole-cell protein patterns as Enterococcus faecalis (7.9%), Ent. mundtii (7.9%), Ent. casseliflavus (5.5%), Ent. faecium (5.2%) and Ent. sulfureus (0.1%). The vast majority of the strains (69.7%) formed a homogeneous 16S rDNA genotype that differed from those of known enterococci. A screening for antagonistic activity using an agar spot test revealed that 18.4% of all isolates were potential antagonists. Partially-purified proteins extracted from cell-free culture supernatant fluids of various species were characterized as pH- and heat-stable bacteriocins active against a wide range of lactic acid bacteria, clostridia and Listeria. The producing strains were antagonistically active even on 'phylloplane agar' at temperatures between 4 and 37 degrees C.
Conclusion:
Enterococci are a common part of the epiphytic microflora of grasses, displaying probably some antagonistic activity.
Significance And Impact Of The Study:
The results provide new information on the distribution, species diversity and antagonistic potential of enterococci in the phyllosphere.